To obtain a better understanding of the effects of electric fields on the fatigue lifetime of PZT materials, specimens of poled and unpoled PZT-8 were either pre-indented to generate a pre-crack or indented in the presence of an applied static electric field. Significant differences in the crack growth behavior perpendicular and parallel to the poling direction were observed in static and time-varying electric fields leading to a reduction in the fracture toughness normal to the poling axis. Fatigue crack growth was significant at field amplitudes as low as 5% of the poling fields. These results are shown to be related to the effects of electrical fields on the stresses at the crack tip.
The reported draft human genome sequence includes many contigs that are separated by gaps of unknown sequence. These gaps may be due to chromosomal regions that are not present in the Escherichia coli libraries used for DNA sequencing because they cannot be cloned efficiently, if at all, in bacteria. Using a yeast artificial chromosome (YAC)/ bacterial artificial chromosome (BAC) library generated in yeast, we found that approximately 6% of human DNA sequences tested transformed E. coli cells less efficiently than yeast cells, and were less stable in E. coli than in yeast. When the ends of several YAC/BAC isolates cloned in yeast were sequenced and compared with the reported draft sequence, major inconsistencies were found with the sequences of those YAC/BAC isolates that transformed E. coli cells inefficiently. Two human genomic fragments were reisolated from human DNA by transformation-associated recombination (TAR) cloning. Re-sequencing of these regions showed that the errors in the draft are the results of both missassembly and loss of specific DNA sequences during cloning in E. coli. These results show that TAR cloning might be a valuable method that could be widely used during the final stages of the Human Genome Project.
It is known that the energy-release rates associated with translation, rotation, and self-similar expansion of cavities or cracks in solids are expressed by path-independent integrals J, L and M, respectively. These integrals are of interest to NDE in that they can be used to characterize nondestructively defects in solids.It is shown that these integrals for a crack may be evaluated by first considering an ellipse and then performing a limiting process. This obviates dealing with singularities at crack tips and holds promise for a more efficient numerical method in complicated cases, since modeling of singularities is always associated with difficulties and uncertainties.
BackgroundSince coronavirus disease 2019 (COVID-19) emerged, increasing cases have been identified worldwide. COVID-19 continues to lead to significant morbidity and mortality, despite developing a vaccination for the disease. While much has been studied regarding the initial presentation and treatment of patients with COVID-19, to our knowledge, no study has uncovered that COVID-19-positive patients with abdominal pain are at a higher risk of requiring intubation.
MethodologyIn this retrospective cohort study, we identified 104 patients who presented to the emergency room of a single tertiary care center with laboratory-confirmed COVID-19 between February 1, 2020, and April 27, 2020, and collected data on reported pain complaints.
ResultsIn this retrospective cohort study, the most common pain complaints were chest pain (25.5%), myalgia (23.4%), and abdominal pain (17.0%). Less common pain complaints included headaches (14.9%) and neck/back pain (6.3%). Of these pain complaints, only patients who reported having abdominal pain were more likely to be intubated (37.5% of patients with abdominal pain were intubated compared to 8.3% of patients without abdominal pain, with a p-value of 0.001).
ConclusionsAbdominal pain in a patient with COVID-19 infection significantly increases their chances of requiring intubation based on the results of this study.
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